Desiccant packaging



Oct- 3, 1950 M. A. cHAvANNEs ET AL 2,524,162

DESICCANT PACKAGING Filed Feb. 27, 1945 jwua/wbo/m, HOWARD Af ROHDIN MARC A. CHAVANN ES FIG. 2

Patented. Oct. 3, 1950 UNITED `STATES PATENT OFFICE DESICCANT PACKAGING Marc Alfred Chavannes, Lisbon, Conn., and

Howard A. Rohdin, Glen Ridge, N. J.

Application February 27, 1945, serial No. 579,986

(ci. x12- 31) 3 Claims.

Itis an object of this invention to provide 'an improved package and an improved method of packaging whereby goods or material may be stored for long periods with complete protection against the ingress of moisture either in the form of water or its vapor.

It is a further object of this invention to provide a package which may be easily inspected to determine 'the extent of moisture penetration, and which may be easily resealed after such inspection.

The above and other objects will be made clear from the following detailed description, taken in connection with the annexed drawings in which:

Figure 1A is a perspective view partly in section of one form of improved package, and

Fig. 2 is a view similar to Fig. 1, of an alternative `form of package.

It is well known that there is no s uch thing as absolutely Vimpervious material, and there is therefore no known package, the walls vof which absolutely will not transmit any moisture vapor. Heretofore it has been common practice to seal such objects as airplane engines, gun mounts, and other highly finished parts in a wrapper or envelope, the vmaterial of which olers good re` sistance to the passage of moist`ure vapor, and to seal within the package a suitable desiccant such, for example, as sili'ca-geljcalciumchloride, or activated carbon. The machine parts are protected against moisture until the desiccant has become saturated. Various means are used to pro-vide visual indication of saturation of the desiccant. These usually involve mixing with the desiccant a suitable anhydrous acid or alkali, together with an anhydrous indicator. As moisture accumulates in the desiccant the acid or alkali is activated to affect the indicator, whereby to bring about a change of color, providing a visual indication that the saturation point has been reached. Y

The materials used for forming packages for thisY purpose are necessarily rugged and opaque, and it is therefore impossible to observe the indicator through such material. Theoretically, a window structure could be devised which would permit inspection. The provision of a window, however, decreases the total resistance of the package to moisture vapor penetration, and moreover, contributes an area of mechanical weakness which is detrimental in handling and shipping the packages.

The fundamental principle of this invention lies in vproviding a duplex package inwhich a desiccant is completely sealed, along with the envelope. A second wrapper is sealed completely around the rst wrapper, and a second body of desiccant is placed between the wrappers. Supercially this appears to be a mere multiplication of parts. In practice, however, it results in protecting the interior ofv the inner wrapper from ingress of moisture vapor and of preventing such ingress for tremendous periods of time. The best sheet materials available for this purpose have a moisture vapor transmission rate slightly under .025 gram of water per hundred square inches per twenty-four hoursvr at 100v degrees Fahrenheit, and with a relative-humidity on the "wet side of per cent; This may seem low, but when it is considered that the total area of the package may easily exceed four thousand times square inches, it is clear that moisture penetration at the total rate of '100 grams every twenty-four hours is a serious factor. Under present practice any reasonable quantity of desiccant may become saturated within about two months; therefore within this time the package must be opened, the desiccant inspected, and perhaps replaced. If for any reason (and there are many reasons) the moisture transmission rate increases, 'there is the distinct possibility that the desiccant will become saturated prior to the regular inspection date, whereupon damage to the'machine parts will ensue.

In the interests of brevity, materials of the character referred to above, which have excellent, but not, of course, perfect resistance to moisture vapor penetration, are characterized herein as unavoidably pervious materials. An example of such a material which is common in the industry comprises a lamination of heat'sealable vinyl resin with an intermediate layer of metallic foil, and an outer layer of scrim. NumerousY other materials having the characteristics Vnoted above may, of course,A be used.

Y inner envelope is so small as to become negligible.

within the inner carton while a second body of desiccant 46 is contained between the inner surface of the outer carton 38 and the outer surface of the inner wrapper 34. Suitable spacers 4B are provided to separate the inner wrapper 34 from the outer carton 38. This is done to facilitate circulation of air and thus to assure uniformity of humidity conditions throughout the space of inner and outer packages. The packages of desiccant 44 and 46 are treated exactly like packages 2U and 22 discussed above in connection with f Fig. 1.

mined, and which probably will not be workedr out for many years to come. Qualitatively, however, there is an abundance of observed data to demonstrate that when the temperature, and especially the humidity, on the high side are low in absolute terms, the rate of transmission is negligible. As a matter of fact, in the testing process, it is necessary to establish the humidity differential between the two sides of the test specimen as high as'the diiierence between one or two per cent on the `low side and ninety-five to ninety-six per cent on the high sidein order to obtain measureable results within 100 hours on a specimen of reasonable size. The decrease in transmission rate Awith decreasing temperature humidity on the high side is far more severe than a' straight line relationship, closely approa-ching Zero per unit of area per unit of time, atlo-w differential, when the high side is low in absolute terms.

In fact, there canbe` imperceptible penetration of moisture through the inner envelope until several weeks after the desiccant between the envelopes has become saturated. This means first, that a longer interval can be allowed between inspections, and second, that, for such greatly increased periods of time, the above m'entioned unpredictable increases in the Vrate of penetration through the outer envelo-pe, under no circumstances', can bringabout the saturation of the desiccant within the inner envelope with consequent damage to the machine parts.

It is still true that from vtime to time the outer envelope must be opened and the outer desiccant inspected and'replaced, but it will not be necessary to open the inner envelope oftener than once in a number of years andthen only as a precautionary measure. In short, so far as protection of the contents is concerned, the present invention do-es not, by doubling the number of walls, merely halve the moisture transmission rate. The number of walls is doubled, but thereby the moisture transmission rate is divided by many times'two. 1

Referring now to Fig. 1, there is shown a commodity lil'surrounded by inner wrapper I2 which in turn is surrounded by an outer wrapper I4. The inner wrapper I2 is hermetically sealed at I5 and the outer wrapper I4'is hermetically sealed 'at i8. A quantity of desiccant 2D is packaged withinthe inner wrapper I2 and another package of desiccant 22 is placed between the wrappers I2 and I4.

In Fig. 2 the arrangement is somewhat different. Here, commodity 301 is contained within a relatively rigid carton 32 formed of cardboard, fibre board or, perhaps, corrugated board. A wrapper 34 of substantially impervious material surrounds the carton 32 and' is hermetically sealed at 35. A second carton 3&3 surrounds the carton 32 and its wrapper 34, while a second wrapper 40 surrounds the carton' 38 and is hermetically sealed at 42. A body of desiccant 44 is contained Each of the quantities of desiccant 20 and 22 (Fig. 1) and 44 and 45 (Fig. 2) is packaged in a bag or wrapper formed of material which is relatively pervious to the transmission of water vapor but relatively impervious to the passage of liquid water. The desiccant, therefore, is enabled to function for the purpose of absorbing water vapor but, as the water accumulates in liquid form in the desiccant, the individual bag or wrapper containing the desiccant tends to prevent liquid water coming in contact either with the commodity or with the adjacent package walls.

There are many materials which are relatively pervious to moisture in the form of vapor, but which are relatively impervious to the passage of water in liquid form; For example, most of the vinylresin lmsehave relatively poor resistance to the passage of moisture vapor, but have excellent resistance to the passage of liquid water. Asa practical matter, however, paper of the high wet strengthV type will-usually be best for this service, since such paper if otherwise untreated offers very low resistance to the vapor, but offers high resistancel tothepassage Vof the liquid. p

It is a vfact that-the apparent moisture vapor transmission rate ofv a given packaging lm increasesxenormously if thereis any actual liquid waterin Contact with eii ,her` surface. This occurs for the reason that any l.packaging material will have a certain quantity, however small, of soluble material. `Liquid water inv Contact with such wrapping material dissolves a portion Aof the soluble matter. Osmosis then immediately takes place, bringing about a passage of the liquid itself. It is, therefore, important to avoid, so far as'possible, any contact of liquid water with the walls of the package. Once in place, there is no functional and Very little structural difference between abag and a wrapper. A bag may, therefore, be regarded as 'a lpartially .preformed and presealed wrapper.

For convenience the term wrapper is used herein, but such term is intended to include bags. The packages illustrated in the drawings have been somewhat idealized and in practice there usually will not be the regularity of form illus trated. Moreover, when the packages are very large, the wrapper will be formed by joining a number of sheets by means of hermetic seals or seams, which may-be of any suitabletypeybut which preferablyshould be made in accordance with the co-pending application ofV Howard A. Rohdin, Serial No. 561,982, -flledfNovember 4, 1944, which has now become. abandoned. The use of spacers between the inner and outer package has been illustrated in connection withv the carton structure of, Fig. 2. It is equally applicable to the wrapper structure of Fig. l, but in practice, where the object is irregular and no carton support is provided, the spacer idea is somewhat more difficult of application.

What is claimed is:- I 1. A' package comprising: a commodity;l an

unavoidably pervious sheet of material wrapped about said commodity and sealed by substantially impervious seals; a quantity of desiccant material enclosed in said wrapper with said commodity; a second wrapper of unavoidably lpervious sheet material surrounding said rst wrapper and sealed by substantially impervious seals; and a quantity of desiccant material enclosed between said rst and second wrappers each of said quantities of desiccant material being wrapped in a material substantially pervious to moisture vapor and substantially impervious to liquid water.

2. A package comprising: a commodity and a quantity of desiccant material enclosed in a substantially rigid carton; a wrapper of unavoidably pervious sheet material sealed by substantially impervious seals around said carto-n; a second carton surrounding said rst carton and its wrapper; and a second wrapper sealed around said second carton; there being a quantity of desiccant material between said second carton and said rst wrapper, each of said quantities of desccant material being wrapped in a material substantially pervious to moisture Vapor and substantially impervious to liquid water.

3. A package comprising: a commodity and a quantity of desiccant material enclosed in a subpervious sheet material sealed by substantially impervious seals around said carton; a second carton surrounding said first carton and its wrapper; and a second wrapper sealed around said second carton; there being a quantity of desiccant material between said second carton and said first wrapper, said second carton being spaced from said first wrapper to provide air circulation therebetween, each of said quantities of desiccant material being wrapped in a material substan tially pervious to moisture vapor and substantially impervious to liquid Water.

VMARC ALFRED CHAVANNES.

HOWARD A. ROHDIN.l

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

